Automatic transmissions contain many gears in various combinations. This may be accomplished via planetary gear sets. The basic planetary gear set consists of a sun gear, a ring gear and two or more planet gears, all remaining in constant mesh. The planet gears are connected to each other through a common carrier which allows the gears to spin on shafts called “pinions” which are attached to the carrier.
One example of a way that this system can be used is by connecting the ring gear to the input shaft coming from the engine, connecting the planet carrier to the output shaft, and locking the sun gear so that it can't move. In this scenario, when we turn the ring gear, the planets will “walk” along the sun gear (which is held stationary) causing the planet carrier to turn the output shaft in the same direction as the input shaft but at a slower speed causing gear reduction (similar to a car in first gear). If we unlock the sun gear and lock any two elements together, this will cause all three elements to turn at the same speed so that the output shaft will turn at the same rate of speed as the input shaft. This is like a car that is in third or high gear. Another way that we can use a Planetary gear set is by locking the planet carrier from moving, then applying power to the ring gear which will cause the sun gear to turn in the opposite direction giving us reverse gear.
Referring now to FIG. 1A, the input shaft 130 for a traditional clutch assembly may be connected to the ring gear 132 while the output shaft 134 is connected to the planet carrier 136 which is also connected to a “multi-disk” clutch pack. The sun gear 138 is connected to a drum 140 which is also connected to the other half of the clutch pack. Surrounding the outside of the drum 140 is a band 112 that can be tightened around the drum 140 (via a servo 142 and an anchor pins 144 disposed in elongated recesses) to prevent the drum 140 with the attached sun gear 138 from turning. It is understood that the servo 142 is controlled by hydraulic pressure. However, the servo 142 and anchor pins 144 for the band 112 take up valuable packaging space in this region of the vehicle. However, it is rather challenging to mount the servo 142 and anchor pins 144 proximate to the drum due to limited vehicle packaging space. Therefore, a robust yet compact clutch assembly is needed.